Staged Fuel Injection Combustor Gap Utilization
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Solution Overview
Problem
Conventional gas turbine combustion systems face limitations in achieving higher firing temperatures while maintaining acceptable NOx emission levels and minimizing aerodynamic pressure losses and leakage, due to the sensitivity of NOx emissions to operating temperatures and combustion characteristics.
Innovation Solution
The implementation of a gas turbine design that includes a combustor coupled with a turbine, featuring a gap at the interface between the combustor and turbine, where a fuel injector is positioned to inject fuel into the airflow passing through the gap, which is expanded to accommodate increased airflow, effectively utilizing a former leakage pathway for staged fuel and air injection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If higher operating temperatures are used to improve engine efficiency, then engine efficiency is improved, but NOx emission levels increase
Solution Approach 1:
The fuel and air injection is divided into multiple axial stages along the combustor length. Primary injection occurs at the forward end, with additional downstream injectors positioned at spaced intervals. This segmentation allows different zones to operate at different temperatures and mixture ratios, enabling higher overall firing temperatures while maintaining lower NOx formation zones through leaner mixtures in downstream regions.
Solution Approach 2:
Different axial zones of the combustor are given different local characteristics through staged injection. The forward zone operates with richer mixtures and higher temperatures for efficient combustion, while downstream zones use leaner mixtures to control NOx formation. This local differentiation of mixture quality and temperature allows the system to achieve high overall efficiency while limiting harmful emissions in specific regions.
2Object-generated harmful factors
If air volume is increased to enable axially staged injection, then emission control is improved, but aerodynamic pressure losses increase
Solution Approach 1:
The injection system transitions from a single-point axial injection to a multi-dimensional staged approach with injectors distributed both axially and radially. Downstream injectors are positioned to utilize the existing airflow pattern and pressure distribution at different axial locations, injecting fuel into regions where the airflow already has favorable properties. This dimensional distribution allows the system to achieve better emission control without proportionally increasing total air volume, thereby limiting aerodynamic penalties.
3Quantity of substance
If leakage pathways are expanded to accommodate increased airflow for staged injection, then airflow requirements are met, but leakage losses increase
Solution Approach 1:
The design accepts and utilizes the inevitable leakage pathways at the combustor-turbine interface rather than attempting to eliminate them. By positioning downstream fuel injectors near these gap regions, the system converts what would be pure leakage losses into useful fuel-air mixing zones. The leaked air, which would otherwise represent a loss, is instead utilized as part of the combustion process in downstream zones, thereby reducing the net penalty of having expanded leakage pathways while still meeting the increased airflow requirements for staged injection.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design enhances engine efficiency by reducing NOx emissions, minimizing aerodynamic pressure losses, and optimizing airflow, allowing for increased firing temperatures without significant emissions penalties.
Implementation Method 1
a fuel injector disposed near the gap for injecting a fuel into an airflow that passes through the gap
Implementation Method 2
combustor coupled to a turbine that together define a working fluid flowpath
Data Source
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AI summary
A gas turbine that includes: a combustor 13 coupled to a turbine 12 that together define a working fluid flowpath 37, the working fluid flowpath extending aftward along a longitudinal axis from a forward end 67 defined by a forward injector 21 in the combustor, through an interface at which the combustor ends and the turbine begins, and then through the turbine to an aftward end; a gap formed at the interface between the combustor 13 and the turbine 12; and a fuel injector 51 disposed near the gap for injecting a fuel into an airflow that passes through the gap. The gap may include a former leakage pathway occurring at the interface. The former leakage pathway may be expanded so to accommodate a desired level for the airflow passing therethrough.